Phone won't mount SD Card

 Pleeeeeeeeeeeeeease help. My Desire HD won't mount the SD card. When I turn the phone on I get the message "removed SD card" I have checked the card and it works fine in a card reader. I have done a factory reset on the phone and I have tried several other working free and nothing works. This all started after I connected my phone to my lap top.
Heeeeeeeeeeeeeeeeelp!  ???It's doing my napper in.........

Hi mate. Tried that but it won't let me unmount............. but thanks for replying.....

Done that........... No change. I've also tried 2 other cards that I know work fine in another HTC phone.......... but keep the suggestions coming........

Am I on a custom wot? So I can format the wot.........? I'm not too up on the technical terms. So as a wise man once said, "come again?" 

Ok, so if I get it right the phone won't read ANY Micro SD card anymore? 

How did you unplug it from the laptop?  HTC phones can be sensitive to that.  Be sure to remove it in the taskbar first ("Safely remove hardware") before you pull out the cable, as simply pulling out the cable is a bit like playing russian roulette.  It'll go just fine most of the time, but occasionally it'll mess up the OS. 

As Sakai says, a factory reset is the best option.  if that doesn't solve the problem, I'd have HTC take a look at the phone.